JP4128386B2 - Exhaust system structure of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
According to the present invention, a pair of two cylinders, a first pair of cylinders adjacent to each other, and a second pair of cylinders arranged side by side on the first pair of cylinders are disposed in the engine body. More specifically, the present invention relates to an exhaust system structure of an internal combustion engine in which each of the pair of cylinders is combusted so that exhaust strokes do not continue to each other, and particularly relates to an arrangement of an exhaust passage and a catalyst device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an in-line four-cylinder internal combustion engine having this type of exhaust system structure, a first direct passage portion extending from a pair of adjacent first cylinder sets and gathering at a collecting portion, and both sides of these first cylinder sets A second direct passage portion extending from the pair of second cylinders and gathering at the gathering portion, and a catalyst device disposed immediately downstream of each gathering portion are known. As described above, the catalyst device is arranged immediately downstream of the collecting portion, that is, at a position relatively close to the internal combustion engine, because the high temperature exhaust gas is supplied to the catalyst in the catalyst device that is in a low temperature state when the internal combustion engine is started. This is to apply gas and thereby activate the catalyst early.
[0003]
[Problems to be solved by the invention]
However, according to the conventional exhaust system structure as described above, since the lengths of the first and second direct passage portions to the respective collecting portions are relatively short, the direction of the exhaust gas when flowing into the collecting portion is set. Exhaust gas tends to flow in an unstable state due to its large nature. For this reason, depending on the positional relationship between each direct passage portion and the collecting portion, there is a tendency that a swirl with strong directivity is generated in the vicinity of the collecting portion or the flow of exhaust gas is biased to a part of the collecting portion. As a result, it is difficult for exhaust gas to hit the catalyst in the catalyst device in a uniform state, and the exhaust gas purification capacity of the catalyst cannot be fully utilized due to being hit in a biased state, which may reduce the catalyst purification rate. There is. For the same reason, the durability of the exhaust gas may decrease because the heat of the exhaust gas strikes the catalyst in a biased state.
[0004]
The present invention has been made to solve the above-described problem, and can apply exhaust gas to the catalyst in the catalyst device in a uniform state, thereby improving the catalyst purification rate and durability of the catalyst. An object of the present invention is to provide an exhaust system structure for an internal combustion engine.
[0005]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 includes a first cylinder set consisting of a pair of cylinders # 2 and # 3 adjacent to each other, and a pair of cylinders # 1 arranged side by side on both sides of the first cylinder set. , # 4 in the engine body (the engine body 2 in the embodiment (hereinafter the same in this section)), and the exhaust stroke in each pair of cylinders of the first and second cylinder groups. Is an exhaust system structure of an internal combustion engine (engine 1) in which combustion is performed so as not to be continuous with each other, and extends from the pair of cylinders # 2 and # 3 of the first cylinder set to the outside of the engine body, respectively, and a collecting portion 10c And a pair of first directly below passage portions 10a and 10b and a pair of cylinders # 1 and # 4 of the second cylinder set that extend substantially horizontally outward from the engine body, and a pair of first directly below passage portions 10a. , a gentle angle than 10b, collecting A pair of second right under passage portion 20a that collectively so as to face each other in parts 20c, and 20b, first and extending from the first and second directly below passage portion 10a, 10b, 20a, 20b of the collecting part 10c, 20c First and second catalyst devices 7, 8 connected to the downstream end portions of the second collecting passage portions 11, 21, and the first and second collecting passage portions 11, 21, respectively, and extending downstream, The pair of first directly below passage portions 10a and 10b are gathered together at the collecting portion 10c at an acute angle than the pair of second directly below passage portions 20a and 20b, and the length X of the first collecting passage portion 11 Is set longer than the length Y of the second collecting passage portion 21, and the space inside the first collecting passage portion 11 is set larger than the space inside the second collecting passage portion 21, and the second The length Y of the collecting passage portion 21 is the first collection It is set shorter than the length X of the passage portion 11, and the center line A of the second collecting passage portion 21 is offset to the engine body side with respect to the center line C2 of the second catalyst device 8. .
[0006]
According to the exhaust system structure of the internal combustion engine, the pair of first direct passage portions extend from the pair of adjacent cylinders, and intersect each other at an acute angle in the gathering portion than the pair of second direct passage portions . In this gathering portion, swirl is likely to occur. In contrast, in the present invention, the first collecting passage unit compares the second collecting passage section, its length is set longer Rutotomoni, the internal space thereof is set large, the collecting portion The distance and space to the first catalyst device are large. Thereby, the swirl described above can be diffused in this space, so that it is possible to prevent the exhaust gas from hitting the catalyst of the first catalytic device in a biased state by the swirl and to uniformly apply the exhaust gas to the catalyst. it can.
[0007]
Further, the pair of second directly below passage portions extend substantially horizontally from the pair of cylinders of the second cylinder set that are spaced apart on both sides of the first cylinder set, and in the collecting portion than the pair of first directly below passage portions. Also gather at a gentle angle so as to face each other . As a result, the exhaust gas flows into the second collecting passage portion without going around along the wall surface of the collecting portion of each second direct passage portion. For this reason, although swirl is unlikely to occur in the collecting portion, in the second collecting passage portion, the exhaust gas tends to flow in a concentrated manner on the side of the peripheral wall portion far from the engine body, so that it becomes a catalyst of the second catalytic device. Is easy to hit in a biased state. On the other hand, in the present invention, since the second collecting passage portion is offset from the second catalyst device to the engine body side, the inflow position of the exhaust gas to the catalyst is shifted to the engine body side, and the exhaust gas is moved to the catalyst body. The exhaust gas can be guided to the central portion, thereby preventing the above-described uneven hitting of the exhaust gas to the catalyst, and exhaust gas can be uniformly applied to the catalyst. As described above, since the exhaust gas can be uniformly applied to the respective catalysts of the first and second catalytic devices, the exhaust gas purification ability of the catalyst can be fully utilized and the catalyst purification rate can be improved. Thus, the exhaust gas characteristics can be improved and the durability of the catalyst can be enhanced.
[0008]
The invention according to claim 2 is the exhaust system structure of the internal combustion engine according to claim 1, wherein the aggregate portion 10c of the first directly below passage portions 10a and 10b has an oval cross section, and a pair of first directly below The passage portions 10a and 10b are arranged such that the center lines D and E of the portions that gather together toward the gathering portion 10c are substantially symmetrical with respect to the major axis L of the ellipse of the gathering portion. .
[0009]
According to this configuration, the pair of first direct passage portions are gathered symmetrically at a certain angle with respect to the major axis in the gathering portion having an oval cross section. For this reason, the exhaust gas from the direct passage portion does not wrap around the wall surface portion with a small curvature of the gathering portion, but easily hits the wall surface portion with a large curvature, so the directivity of the exhaust gas is weakened and the swirl is further reduced. Can be suppressed. Therefore, the exhaust gas characteristics can be further improved and the durability of the catalyst can be further improved. In addition, since the pair of first direct passage portions are gathered symmetrically with respect to the major axis of the gathering portion, the above-described action can be obtained in both the pair of first direct passage portions. Note that the oval here includes both an ellipse and an oval shape.
[0010]
According to a third aspect of the present invention, in the exhaust system structure of the internal combustion engine according to the first or second aspect, at least one of the aggregate portions 10c, 20c of the first and second direct passage portions 10a, 10b, 20a, 20b is provided. The exhaust gas sensors 6 and 6 are further provided and detect the state of the exhaust gas discharged from the corresponding cylinder set, and the exhaust gas sensors 6 and 6 are disposed on the center lines C1 and C2 of the corresponding catalyst device. It is characterized by that.
[0011]
According to this configuration, the exhaust gas sensor is disposed in the central portion of the corresponding catalyst device, that is, at the center of the flow of the exhaust gas, at the aggregate portion of the first and / or second direct passage portions. Therefore, a representative state of the exhaust gas can be detected by the exhaust gas sensor. Therefore, since the state of the exhaust gas in each cylinder can be detected with high accuracy, the exhaust gas characteristics can be further improved, for example, by performing air-fuel ratio control of the internal combustion engine in accordance with the output of the exhaust gas sensor. .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. 1 to 7 schematically show an exhaust system structure of an internal combustion engine to which the present invention is applied. As shown in FIG. 1, the internal combustion engine (hereinafter referred to as “engine”) 1 is an in-line four-cylinder engine in which four cylinders # 1 to # 4 are arranged in order, and has these cylinders # 1 to # 4. An engine main body 2 (engine main body) and an exhaust manifold 3 that is attached to the engine main body 2 and guides the exhaust gas discharged from the cylinders # 1 to # 4 to the downstream side while gathering. In the engine 1, combustion is performed in the order of cylinders # 1, # 3, # 4, and # 2.
[0013]
The manifold 3 includes a first manifold section 4 communicating with a pair of central cylinders # 2 and # 3 (first cylinder group) adjacent to each other, and a pair of cylinders # 1 on both sides of the cylinders # 2 and # 3. And a second manifold portion 5 communicating with # 4 (second cylinder group). The first and second manifold sections 4 and 5 are provided with exhaust gas sensors 6 and 6, respectively, and the first and second catalyst devices 7 and 8 are provided on the downstream sides of the exhaust gas sensors 6 and 6, respectively.
[0014]
The first manifold section 4 is connected to the pair of cylinders # 2 and # 3 via an exhaust port (not shown) and upstream connection ports 9 and 9, and extends outward from the engine body 2 and downstream. A pair of first directly below passage portions 10a and 10b that gather together at the gathering portion 10c at the end, and a first gathering passage portion 11 that extends from the gathering portion 10c and guides exhaust gas to the first catalyst device 7 are provided. Yes.
[0015]
The first direct passage portions 10a and 10b have predetermined curved shapes and lengths, respectively. Specifically, the first directly below passage portion 10a connected to the cylinder # 2 extends obliquely upward from the connection port 9 and is predetermined at a substantially right angle from the connection port 9 to the engine body 2 in plan view. It extends in length, curves from the middle to the cylinder # 3 side, and extends so as to be largely inclined. The first direct passage portion 10b connected to the cylinder # 3 extends obliquely upward from the connection port 9 in the same manner as the first direct passage portion 10a, and from the connection port 9 to the engine body 2 in plan view. It extends a predetermined length substantially at a right angle, and extends slightly obliquely toward the cylinder # 4 from the middle. As a result, the first direct passage portions 10a and 10b are gathered at a relatively acute angle at the gathering portion 10c. The collecting portion 10c is located above the connection ports 9 and 9, and is slightly located closer to the cylinder # 4 than the connection port 9 with the cylinder # 3 in plan view.
[0016]
As shown in FIG. 2, the collective portion 10c has an oval cross-sectional shape. The downstream portions of the first direct passage portions 10a and 10b are connected to the collecting portion 10c so that their center lines D and E are symmetrical with each other at a predetermined angle with respect to the major axis L of the oval cross section of the collecting portion 10c. Have gathered. A sensor mounting hole 10d is formed at a predetermined position on the upper wall of the collective portion 10c, and the exhaust gas sensor 6 is positioned on the center line C1 of the first catalyst device 7 in the sensor mounting hole 10d. It is attached (see FIG. 6). The exhaust gas sensor 6 linearly detects the oxygen concentration (air-fuel ratio) in the exhaust gas.
[0017]
The first collecting passage portion 11 has a constant cross section, has the same oval shape as the cross section of the collecting portion 10c (see FIG. 1), is slightly inclined from the collecting portion 10c when viewed from the side, and is relatively downward. It extends long and has a predetermined length X (see FIGS. 3 and 4). Thus, since the first collecting passage portion 11 is relatively long, a relatively large distance and space are secured between the collecting portion 10c and the first catalyst device 7.
[0018]
The first catalyst device 7 has a cylindrical case 30 and a three-way catalyst 41 (only the second catalyst device 8 is shown) accommodated in the case 30. The case 30 is connected to the downstream end portion of the first collecting passage portion 11 and extends slightly obliquely concentrically therewith. The three-way catalyst 41 has a honeycomb-shaped cross section and is activated at a predetermined temperature (for example, 300 ° C.) or higher, thereby causing harmful substances (HC, CO, and NOx) in exhaust gas passing through the first catalyst device 7. Is purified by oxidation / reduction action.
[0019]
The second manifold portion 5 is connected to the pair of cylinders # 1 and # 4 via an exhaust port (not shown) and upstream connection ports 9 and 9 and extends outward from the engine body 2 and has a downstream end. And a second collecting passage portion 21 extending from the collecting portion 20c and leading the exhaust gas to the second catalytic device 8. .
[0020]
The second direct passage portions 20a and 20b have predetermined curved shapes and lengths, respectively. Specifically, the second directly below passage portion 20a connected to the cylinder # 1 extends substantially horizontally and slightly extends from the connection port 9 to the engine main body 2 at a substantially right angle in plan view. To the cylinder # 2 side obliquely. Similarly to the second direct passage portion 20a, the second direct passage portion 20b connected to the cylinder # 4 extends substantially horizontally and is slightly perpendicular to the engine body 2 from the connection port 9 when seen in a plan view. From the middle of the passage, it passes through the lower side of the first direct passage portions 10a, 10b, and extends obliquely relatively long toward the cylinder # 3. As a result, the second directly below passage portions 20a and 20b gather at the gathering portion 20c so as to face each other at a gentler angle than the first directly below passage portions 10a and 10b. The collecting portion 20c is located at substantially the same height as the connection ports 9 and 9 and faces the connection port 9 of the cylinder # 2 in plan view.
[0021]
A sensor mounting hole 20d is formed at a predetermined position on the upper wall of the collective portion 20c, and the exhaust gas sensor 6 is mounted in the sensor mounting hole 20d so as to be positioned on the center line C2 of the second catalyst device 8. (See FIG. 7). The second collecting passage portion 21 extends downward, and the length Y of the second collecting passage portion 21 is smaller than the length X of the first collecting passage portion 11 by the amount that the collecting portion 20c is lower than the collecting portion 10c, as shown in FIG. Is also shorter.
[0022]
The second catalyst device 8 is configured in the same manner as the first catalyst device 7, and includes a cylindrical case 40 and a three-way catalyst 41 (see FIG. 4) accommodated in the case 40. Further, as shown in FIG. 5, the second catalyst device 8 has the second collecting passage portion 21 so that the center line A of the second collecting passage portion 21 is offset toward the engine body 2 with respect to the center line C2. It is connected to the.
[0023]
According to the exhaust system structure having the above configuration, the exhaust gas from the cylinders # 1 to # 4 of the engine 1 is discharged as follows. That is, on the first manifold section 4 side, the exhaust gas discharged from the cylinder # 2 flows into the first direct passage section 10a, and then enters the collecting section 10c with a predetermined length with respect to the long diameter L of the oval cross section. It flows in with an angle, and does not go around the wall surface portion with a small curvature of the collective portion 10c, but easily comes into direct contact with the wall surface portion with a large curvature. Thereby, the directivity of the exhaust gas is weakened, and swirl when flowing into the collecting portion 10c is sufficiently suppressed. The exhaust gas passes through the first collecting passage portion 11 that is longer than the second collecting passage portion 21, thereby being guided to the first catalyst device 7 in a sufficiently diffused state. As described above, the exhaust gas can be uniformly applied to the three-way catalyst of the first catalyst device 7. Further, as described above, the first directly below passage portion 10b is disposed in the collecting portion 10c symmetrically with respect to the long diameter L of the collecting portion 10c, and thus is discharged from the cylinder # 3. Similarly, the exhaust gas can be sufficiently applied to the three-way catalyst while sufficiently suppressing the swirl when flowing into the collecting portion 10 c and being sufficiently diffused by the first collecting passage portion 11.
[0024]
On the second manifold portion 5 side, the exhaust gas discharged from the cylinders # 1 and # 4 flows into the corresponding second directly below passage portions 20a and 20b, and then passes through the collecting portion 20c to the second collecting passage portion. 21 concentrates on the peripheral wall portion side far from the engine body 2. As described above, since the second collecting passage portion 21 is offset toward the engine body 2 with respect to the second catalyst device 8, the exhaust from the second collecting passage portion 21 to the three-way catalyst 41 of the second catalyst device 8. The inflow position of the gas can be shifted to the engine body 2 side, and the exhaust gas can be guided to the center of the three-way catalyst 41. As described above, the exhaust gas can be uniformly applied to the three-way catalyst 41.
[0025]
As a result, exhaust gas can be uniformly applied to the three-way catalysts 41, 41 of the first and second catalyst devices 7, 8, so that the exhaust gas purification ability of each three-way catalyst 41 can be fully utilized. By improving the catalyst purification rate, the exhaust gas characteristics can be improved, and the durability of each three-way catalyst 41 can be increased.
[0026]
Further, the exhaust gas sensors 6 and 6 are arranged in the collecting portions 10c and 20c so as to be positioned on the center lines C1 and C2 of the first and second catalyst devices 7 and 8, that is, at the center of the exhaust gas flow, respectively. Therefore, a representative state of the exhaust gas can be detected by the exhaust gas sensors 6 and 6. Therefore, the state of the exhaust gas in the cylinders # 1 to # 4 can be accurately detected. For example, by performing air-fuel ratio control of the engine 1 according to the output of each exhaust gas sensor 6, the exhaust gas characteristics can be further improved. Can be improved.
[0027]
In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the present embodiment, the cross section of the collective portion 10c is formed in an oval shape, but it may be formed in an oval shape. Moreover, you may provide the exhaust gas sensor 6 provided in both the 1st and 2nd manifold parts 4 and 5 in any one of these. Further, the embodiment is an example in which the present invention is applied to an in-line four-cylinder internal combustion engine, but the present invention can also be applied to other appropriate types. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.
[0028]
【The invention's effect】
As described above, according to the exhaust system structure of the internal combustion engine of the present invention, exhaust gas can be applied to the catalyst in the catalyst device in a uniform state, thereby improving the catalyst purification rate and durability of the catalyst. It has the effect of being able to.
[Brief description of the drawings]
FIG. 1 is a partial schematic perspective view of an internal combustion engine to which an exhaust system structure of the present invention is applied.
FIG. 2 is a plan view of a manifold and first and second catalytic devices.
FIG. 3 is a front view of a manifold and first and second catalytic devices.
FIG. 4 is a side view of the manifold and the first and second catalytic devices.
FIG. 5 is a partial side view of a manifold and first and second catalytic devices.
FIG. 6 is a partial perspective view of the first manifold section and the first catalyst device.
FIG. 7 is a partial front view of a second manifold section and a second catalyst device.
[Explanation of symbols]
1 Internal combustion engine 2 Engine body (engine body)
# 2, # 3 A pair of cylinders (first cylinder set)
# 1, # 4 A pair of cylinders (second cylinder set)
6 Exhaust gas sensor 7 First catalyst device 8 Second catalyst device 10a, 10b First directly below passage portion 10c Collecting portion 11 First collecting passage portion 20a, 20b Second immediately below passage portion 20c Collecting portion 21 Second collecting passage portion X First Length Y of the collecting passage portion Length A of the second collecting passage portion Center line C2 of the second collecting passage portion Center line D of the second catalytic device Center line E downstream of the first immediately below passage portion First straight passage portion Center line L of the downstream part of the major axis C1 of the cross section of the gathering part Center line of the first catalytic device

Claims (3)

A first cylinder set comprising a pair of cylinders adjacent to each other and a second cylinder set comprising a pair of cylinders arranged side by side on both sides of the first cylinder set are provided in the engine body. An exhaust system structure of an internal combustion engine in which combustion is performed so that exhaust strokes are not continuous with each other in each of the pair of cylinders of
A pair of first direct passage portions extending from the pair of cylinders of the first cylinder set to the outside of the engine body and gathering together at a gathering portion;
A pair that extends substantially horizontally from the pair of cylinders of the second cylinder set to the outside of the engine body , and gathers so as to face each other at a gathering portion at a gentler angle than the pair of first direct passage portions. A second direct passage section of
First and second collecting passage portions extending from the collecting portion of the first and second direct passage portions, respectively;
First and second catalyst devices connected to the downstream end portions of the first and second collecting passage portions, respectively, and extending downstream,
The pair of first direct passage portions are gathered at the gathering portion at an acute angle than the pair of second direct passage portions,
The length of the first collecting passage portion is set to be longer than the length of the second collecting passage portion, and the space inside the first collecting passage portion is larger than the space inside the second collecting passage portion. Is also set larger,
The length of the second collecting passage portion is set shorter than the length of the first collecting passage portion,
An exhaust system structure for an internal combustion engine, wherein a center line of the second collecting passage portion is offset toward the engine body with respect to a center line of the second catalytic device. The gathering portion of the first direct passage portion has an oval cross section,
The pair of first direct passage portions are arranged such that center lines of portions that gather together toward the gathering portion are substantially symmetrical with respect to a major axis of the ellipse of the gathering portion. The exhaust system structure for an internal combustion engine according to claim 1. An exhaust gas sensor that is provided in at least one of the aggregate portions of the first and second direct passage portions and detects the state of exhaust gas discharged from the corresponding cylinder set;
The exhaust system structure for an internal combustion engine according to claim 1 or 2, wherein the exhaust gas sensor is arranged on a center line of the corresponding catalyst device.

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